Design And Implementation Of Functional Waveguide Based On Digital Metastructures

With the development of silicon photonics technology,the basic silicon waveguide devices have been deeply studied and their footprint and performance tend to be stable,which limits the integration of silicon photonic devices in recent years.With the rapid development of optical interconnects and communications,the scaling of data throughput and functionalities per unit chip area in a silicon photonics drive the need for a large-scale integrated photonic chip with a dense layout.Bends and tapers are the most commonly used components in integrated optics and systems.Bends have been included in many silicon photonic multi-project wafer design kits.Taper waveguides with sub-micron cross sections have been widely used for on-chip interconnects and functional photonic integrated circuits.This paper have optimized and designed silicon waveguide devices such as ultra-small bends and waveguide tapers aim at the demand for high integration of PIC.For the requirements of high performance and small size,a design scheme based on digital metastructures is proposed.This paper realizes an ultra-compact attenuator with any stable attenuation value and optimizes the design of ultra-small radius bend waveguides and designs the waveguide taper of the digital superstructure.Here also shows the application of a designed taper structure and the grating to form a grating coupler.And it is compared with focus and linear taper grating coupler to prove its feasibility.All devices follow the same design,preparation,and measurement process: Silicon waveguide devices are modeled according to the design requirements,and the optimized region is equally divided into square pixels,which has two material properties.Different pixel arrangements can achieve different device performance.The inverse optimization algorithm can automatically design the pixel arrangement to achieve the target performance.3D FDTD method is used to simulate the designed structure to obtain optical field and transmission efficiency to view the optimization effect.The devices were fabricated experimentally,and the processes of slicing,cleaning,coating,electron beam exposure,developing and fixing,inductively coupled plasma etching and decorating were sequentially performed in accordance with the experimental process.Then,scanning electron microscope confirm the structure and size of fabricated device.An optical fiber-on-chip coupling test platform was set up and each device was accurately measured.Cascaded fabrication of designed structures with high transmission efficiency was needed to reduce measurement errors and the measurement data was normalized.The measurement data is normalized to obtain the experimental efficiency and compared with the simulation data.And analyze and compare the performance and robustness of the device.All silicon waveguide devices in this paper are designed for C-bands and TE modes.Design methods and structures also allow TM mode and other spectral bands.In this paper,the size of the designed silicon waveguide device is the smallest and the performance is very high compared with the devices that have been reported so far,and all of device are fabricated successfully.The experimental performance is consistent with the simulation.The optimal design of digital-metastructures breaks through the size limitations of traditional silicon waveguide devices and has potential application value in integrated optical devices and systems.